Multi-lumen catheter

ABSTRACT

The invention provides a catheter for placement within a vessel of a patient. The catheter comprises an elongated catheter body, a septum extending longitudinally through the interior of the catheter body from the dividing the interior of the catheter body into a first lumen and a second lumen. Each lumen has curved or angled internal walls at the distal end of the catheter that terminate at ports located on opposing sides of the catheter body. The invention also provides a method for exchanging fluids in a patient comprising the step of positioning the catheter of the present invention in communication with a fluid-containing vessel of a patient. The method is particularly well-suited for hemodialysis, plasmapheresis, and other therapies which require removal and return of blood.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/453,663, filed Apr. 23, 2012, which claims the priority benefit ofU.S. provisional application No. 61/477,815, filed Apr. 21, 2011, and isa continuation-in-part of U.S. patent application Ser. No. 12/479,257,filed Jun. 5, 2009, now U.S. Pat. No. 8,517,978, which is a continuationof U.S. patent application Ser. No. 11/103,778, filed Apr. 12, 2005, nowU.S. Pat. No. 7,569,029, which claims the benefit of U.S. provisionalapplication Ser. No. 60/561,430, filed Apr. 12, 2004, each of which isincorporated herein by reference in their entireties.

BACKGROUND

The present invention relates to a multi-lumen catheter and, morespecifically, to a dual-lumen catheter with entry and exit ports havingcurved or angled walls to direct the flow of fluids therethrough.

Dual-lumen catheters have been available for many years for a variety ofmedical purposes. It is only in recent years, however, that suchcatheters have been developed for use in hemodialysis and othertreatments which involve the removal and replacement of blood. Thegeneral form of dual-lumen catheters goes back to as early as 1882 whenPfarre patented such a catheter in the United States under Ser. No.256,590. This patent teaches a flexible dual-lumen catheter which isused primarily for cleaning and drainage of, for example, the bladder,rectum, stomach and ear. In this type of catheterization, the catheteris introduced into an existing body orifice without the use of anypuncturing needle or guide wire.

More recently, a catheter was developed and patented by Blake et al.under U.S. Pat. No. 3,634,924. This patent teaches a double lumencardiac balloon catheter which is introduced into a large vein and theballoon is inflated to control the flow in the vein. The catheter can beplaced by using the balloon as a “sail” to move with the blood from anante-cubital or other peripheral vein through for example, the rightheart chambers into the smaller radicals of the pulmonary artery wherethe catheter takes up its intended function. This patent teaches the useof two lumina in a single body and explains how to make a tip for adual-lumen structure of the type which has become common for a varietyof purposes including hemodialysis. The structure uses a plug to sealthe end of one lumen and a wire which retains the shape of the otherlumen during formation of the tip in a heated die.

Further patents which teach dual-lumen or multiple lumen catheters forgeneral use include the following: U.S. Pat. Nos. 701,075; 2,175,726;2,819,718; 4,072,146; 4,098,275; 4,134,402; 4,180,068; 4,406,656;4,451,252; 5,221,255; 5,380,276; 5,395,316; 5,403,291; 5,405,341;6,001,079; 6,190,349; 6,719,749; 6,758,836; and 6,786,884, thedisclosures of each of which are incorporated herein in their entirety.

Vascular catheter access techniques have been known to the medicalprofession for many years and, in fact, can be traced back to the 17thcentury. However, it was only with the introduction of the Seldingertechnique in the early 1950s that a new approach could be used toimprove vascular access. This technique was taught in an articlepublished by Dr. Sven Ivar Seldinger resulting from a presentation madeat the Congress of the Northern Association of Medical Radiology atHelsinki in June of 1952. The technique essentially involves the use ofa hollow needle to make an initial puncture, and a wire is then enteredthrough the needle and positioned in the vessel. The needle is withdrawnand the catheter is entered percutaneously over the wire which is itselflater withdrawn. With this technique it became possible to make lesstraumatic vascular access and this has now become the accepted method ofperforming access in numerous medical techniques. One of thesetechniques which been the subject of much research and development ishemodialysis.

Hemodialysis can be defined as the temporary removal of blood from apatient for the purpose of extracting or separating toxins therefrom andthe return of the cleansed blood to the same patient. Hemodialysis isindicated in patients where renal impairment or failure exists, that is,in cases where the blood is not being properly or sufficiently cleansed,particularly to remove waste materials and water, by the kidneys.

In the case of chronic renal impairment or failure, hemodialysis has tobe carried out on a repetitive basis. For example, in end-stage kidneydisease where transplantation of kidneys is not possible or for medicalreasons is contra-indicated, the patient may have to be dialyzed about100 to 150 times per year. This can result in several thousand accessesto the blood stream to enable hemodialysis to be performed over theremaining life of the patient.

Towards the end of 1960, Dr. Stanley Shaldon and colleagues developed,in the Royal Free Hospital in London, England, a technique forhemodialysis by percutaneous catheterization of deep blood vessels,specifically the femoral artery and vein. The technique was described inan article published by Dr. Shaldon and his associates in the Oct. 14,1961 edition of The Lancet at Pages 857 to 859. Dr. Shaldon and hisassociates developed single lumen catheters having tapered tips forentry over a Seldinger wire to be used in hemodialysis. Subsequently,Dr. Shaldon and his colleagues began to insert single lumen inlet andoutlet catheters in the femoral vein and this was reported in theBritish Medical Journal of Jun. 19, 1963. The purpose of providing bothinlet and outlet catheters in the femoral vein was to explore thepossibility of a “self-service” approach to dialysis. Dr. Shaldon wassubsequently successful in doing this and patients were able to operatereasonably normally while carrying implanted catheters which could beconnected to hemodialysis equipment periodically.

An advantage of dual-lumen catheters in hemodialysis is that only onevein access need be affected to establish continued dialysis of theblood. One lumen serves as the conduit for blood flowing from thepatient to the dialysis unit and the other lumen serves as a conduit fortreated blood returning from the dialysis unit to the patient. Thiscontrasts with prior systems where either two insertions were necessaryto place two separate catheters as was done by Dr. Shaldon, or a singlecatheter was used with a complicated dialysis machine which alternatelyremoved blood and returned cleansed blood.

The success of Dr. Shaldon in placing catheters which will remain inplace for periodic hemodialysis caused further work to be done withdifferent sites. Dr. Shaldon used the femoral vein, and in about 1977Dr. P. R. Uldall, in Toronto Western Hospital, Canada, began clinicaltesting of a subclavian catheter that would remain in place betweendialysis treatments. An article describing this was published by Dr.Uldall and others in Dialysis and Transplantation, Volume 8, No. 10, inOctober 1979. Subsequently Dr. Uldall began experimenting with a coaxialdual-lumen catheter for subclavian insertion and this resulted inCanadian Patent No. 1,092,927 which issued on Jan. 6, 1981. Althoughthis particular form of catheter has not achieved significant success inthe marketplace, it was the forerunner of dual-lumen catheters implantedin the subclavian vein for periodic hemodialysis.

The next significant step in the development of a dual-lumen catheterfor hemodialysis is Canadian Patent No. 1,150,122 to Martin. Asubsequent development is shown in U.S. Pat. No. 4,451,252 also toMartin. This catheter utilizes the well-known dual-lumen configurationin which the lumina are arranged side-by-side separated by a diametricseptum. The structure shown in this patent provides for a tip making itpossible to enter a Seldinger wire through one of the lumina and to usethis wire as a guide for inserting the catheter percutaneously. Thistype of structure is shown in a European Patent Application to Edelmanpublished under No. 0 079 719, and in U.S. Pat. Nos. 4,619,643;4,583,968; 4,568,329; 4,543,087; 4,692,141; 4,568,329, and U.S. Des.Pat. No. 272,651, the disclosures of each of which are incorporatedherein in their entirety.

In order to insert a catheter over a guide wire using the Seldingertechnique, or indeed any similar technique, the tip of the catheter mustpossess sufficient rigidity so that it does not concertina as itcontacts the skin because this would enlarge the skin puncture as thecatheter is being entered over the wire. To some extent this is at oddswith the desirable material qualities of the main body of catheter whichshould be soft and flexible for patient comfort. In an effort to solvethis problem, a variety of tips have been formed within the limitationsof using a single extrusion from which the body and tip are formed. Theresult is that the tips have in general been made by using some of theexcess material found in the shorter intake lumen. This has led to otherproblems such as very stiff tips which are unsuitable for prolongedplacement in a vein; voids which can accumulate stagnant blood; andshort stubby tips which are less desirable for insertion than longermore gradual tips. Also, because there is not always sufficient materialto form the tip, plugs have been added with a varying degree of successbecause if the plug is not placed accurately the resulting structure mayhave unacceptable spaces where blood can stagnate.

It must also be recognized that the degree of rigidity in the tipbecomes more important if the catheter is to reside in the patient forprolonged periods, as is becoming more common in many treatments,notably hemodialysis. This is because although ideally the catheter liesin the middle of the vein, in practice it will often bear against thevessel wall. In such circumstances it is possible that a stiff tip coulddamage or even embed itself in the vessel wall when left in place forextended periods.

Hemodialysis, as practiced today, normally employs one of two types ofcatheters to remove blood from the patient for processing and returnprocessed blood to the patient. Most commonly, a dual-lumen catheter isused, each lumen having either a generally cylindrical orsemi-cylindrical configuration. Alternatively, two separate tubes, eachusually having a full cylindrical configuration, are used separately toremove blood for dialysis and return the processed blood.

Flow rates possible with conventional dual-lumen catheters are usuallylower than those achievable where separate tubes are used to removeblood from a vein for dialysis and then return processed blood back tothe vein. Thus, the use of two tubes has become more and more popular asthe capacity (maximum flow rate) of hemodialysis membranes hasincreased.

Hemodialysis membranes are now able to process blood at over 500 ml offlow per minute. Even higher processing rates are foreseeable. However,problems occur with both the line introducing purified blood back intothe vein and the line removing blood for purification at flow ratesabove 300 ml per minute. A high flow rate from the venous line may causewhipping or “firehosing” of the tip in the vein with consequent damageto the vein lining A corresponding high flow rate into the arterial linemay cause the port to be sucked into the vein wall, resulting inocclusion.

The rate of flow through a catheter lumen, whether it be in a singlelumen or a dual-lumen catheter, is controlled by a number of factorsincluding the smoothness of the wall surface, the internal diameter orcross-sectional area of the tube lumen, and the length of the tubelumen. The most important factor is the cross-sectional area of the tubelumen. The force or speed of the fluid flow in a tube lumen for a givencross-sectional area is controlled by the external pumping force. Thisis a positive pressure pushing processed blood through the venous lumenand a negative (suction) pressure pulling unprocessed blood through thearterial lumen.

Problems encountered in providing for a high flow rate through acatheter are magnilied in a dual-lumen catheter construction. Becauseeach of the lumina in a dual-lumen catheter normally has a D-shape, ithas been assumed that flow rates are limited. Furthermore, suchdual-lumen catheters are, to a great extent, catheters with a main portwhich opens at the end of a lumen substantially on the axis of thelumen. Thus, firehosing frequently results. Firehosing may damage thevein wall, triggering the build-up of fibrin on the catheter tip. Fibrinbuild-up may further result in port occlusion.

There are dual lumen-catheters which utilize side ports for both outflowand inflow. An example is the catheter disclosed in U.S. Pat. No.5,571,093 to Cruz et al. However, such catheters have not been entirelysuccessful in solving problems related to hemodialysis with dual lumencatheters, e.g., high incidences of catheter port occlusion as well assome degree of fire-hosing. Further, the abrupt change in direction ofthe flow of blood from the vein into the catheter can result in traumaand damage to red blood cells, especially at higher flow rates.

SUMMARY

This disclosure is not limited to the particular systems, devices andmethods described, as these may vary. The terminology used in thedescription is for the purpose of describing the particular versions orembodiments only, and is not intended to limit the scope.

As used in this document, the singular forms “a,” “an,” and “the”include plural references unless the context clearly dictates otherwise.Unless defined otherwise, all technical and scientific terms used hereinhave the same meanings as commonly understood by one of ordinary skillin the art. Nothing in this document is to be construed as an admissionthat the embodiments described in this document are not entitled toantedate such disclosure by virtue of prior invention. As used in thisdocument, the term “comprising” means “including, but not limited to.”

An object of the present invention is to provide an improved multi-lumencatheter for use in hemodialysis, plasmapheresis, and other therapieswhich require removal of blood from one lumen of the catheter and returnof treated blood through the other lumen.

Another object is to provide a multi-lumen catheter which is capable ofaccommodating high flow rates.

Yet another object is to provide a more efficient multi-lumen catheterfor use in hemodialysis, plasmapheresis, and other therapies whichrequire removal of blood from one lumen of the catheter and return oftreated blood through the other lumen.

Still another object is to provide a multi-lumen catheter which permitshigh flow rates while reducing trauma to vessel walls and red celldamage.

Yet another object of the present invention is a multi-lumen catheterhaving a tip configuration which minimizes recirculation by maximizingthe control and direction of blood flow into and out from the lumenports.

The foregoing and other objects are realized in accord with the presentinvention by providing an apparatus which comprises an elongatedcatheter body for placement within a vessel, a septum that runslongitudinally through the interior of the catheter body so as to dividethe interior of the catheter body into a first lumen and a second lumeneach having a distal end having curved or angled internal walls thatterminate at ports located on opposing sides of the catheter body. Thecurved or angled internal walls at the distal end of the lumina providefor a transition zone in which the flow of blood into and out from thecatheter travels a path that gradually changes the direction of the flowof fluids between the direction of flow in the lumen and the directionof flow in the vessel.

In one embodiment, the change in direction of the flow pattern into andout of the catheter body is substantially helical. In other embodiments,the direction of the flow pattern into and out of the catheter body iscurved, and in still other embodiments the direction of the flow patterninto and out of the catheter body is angled. In this manner, the flowpatterns of these embodiments provide for more efficient exchange ofblood by creating an alternate pattern of blood dynamics through thecatheter lumina and the vessel.

In another embodiment, the ports of the lumina are longitudinallyspaced. In this manner the withdrawal of blood to be treated and thereturn of treated blood are further separated so as to advantageouslyminimize the recirculation of treated blood with untreated blood. Thelength of separation may vary according with specific application, andis preferably from about 2 to about 3 centimeters. Preferably, the lumenport associated with the withdrawal of blood from the patient is“upstream” of the lumen port associated with the return of treatedblood.

These and other features of the invention will be more fully understoodby reference to the following drawings and the detailed description setforth below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a perspective view of a dual-lumen catheter of thepresent invention attached to inflow and outflow tubing.

FIG. 2 illustrates a cross-sectional view of a dual lumen catheter ofFIG. 1

FIG. 3 illustrates a perspective view of a dual-lumen catheter of thepresent invention shown apart from inflow and outflow tubing.

FIG. 4 illustrates another perspective view of the dual-lumen catheterof FIG. 3.

FIG. 5 illustrates a third perspective view of the dual-lumen catheterof FIG. 3.

FIGS. 6A-6D illustrate an alternative embodiment of a split tipmulti-lumen catheter.

FIGS. 7A-7E illustrate an alternative embodiment of a step tipmulti-lumen catheter.

FIGS. 8A-8E illustrate an alternative embodiment of a symmetrical tipmulti-lumen catheter.

FIGS. 9A-9D illustrate an alternative embodiment of a symmetrical tipmulti-lumen catheter having a spiral twisting septum.

DETAILED DESCRIPTION

In accordance with the apparatus of the present invention, there isprovided a catheter body that is adapted for insertion into a vessel ofa patient such as, for example, a vein. The catheter body comprises anexternal wall and a septum extending longitudinally along the internallength of the catheter body to define two substantially parallel luminaeach having an internal wall and a port located at the side of thedistal end thereof.

At the distal end of each lumen, at least a portion of the internalwalls of the lumina are curved or angled to define a transition zoneterminating at the port. So configured, the transition zone permits theflow of fluids traveling the length of the lumen to be graduallydeflected from the longitudinal direction of the lumen to the transversedirection of the side-facing port at the distal end thereof.

For fluids entering the side-facing port of the lumen, the transitionzone permits the flow to be gradually deflected from the direction oftravel through the vessel through the lateral direction of entry to thelongitudinal direction of travel in the lumen. In this fashion, thetransition zone provides a gradual change in the direction of flow intoand out of the lumina. This smoother and more physiologic change ofdirection of the fluids traveling through the lumina decreasesfirehosing of the catheter tip during high rates of fluid exchange,reduces stresses experienced by the fluid, and permits a more efficientand higher rate of flow into and out from the catheter. This moregradual change in direction of blood flow also results in lessprolongation of blood residence time within the catheter tips which candecrease the likelihood of thrombus formation within the catheter. Inthe context of hemodialysis, plasmapheresis, and other therapies whichrequire the transport of blood, decrease in stress provided by thetransition zones at the distal end of the lumina decreases the incidenceof platelet activation, hemolysis and trauma to the vessel lining.

In one embodiment, a first lumen of the catheter terminates in a firstbolus cavity, which is formed into one side of a bolus tip at a positionbetween the interfacing section of the lumen and a nose section of thebolus tip. The nose section of the terminal portion of the first lumenmay be formed through an injection molding process to create a helicalshape of the nose section and first bolus cavity so that fluids such asblood traveling through the lumen have a smooth transition of itsdirection of flow as it enters the first lumen. The second lumen of thecatheter terminates in a second bolus cavity oriented 180° from thefirst bolus cavity, and possesses a nose section which has a similarinjection molded-configuration as the nose tip of the first lumen. Thenose sections of the first and second lumina direct blood flow indirections opposite to each other thereby reducing the admixture oftreated blood with non-treated blood. Preferably, the second lumen inthis embodiment extends beyond the first lumen by about 2 to about 3centimeters so that the nose section of the terminal portion of thesecond lumen is longitudinally spaced from the nose section of theterminal portion of the first lumen.

In another embodiment, the terminations of the first and second luminawithin the nose section are partly recessed, to enable the overhangingaspect of the nose section to serve as a barrier with the vessel wall.This design is intended to reduce the phenomenon of partial or totalocclusion of the lumina of the catheter.

In yet another embodiment, an additional lumen is provided within thecatheter body to allow introduction of a guide wire. The guide wireinserted into this additional lumen and used to assist in theintroduction and proper placement of the catheter tip into a vessel of apatient. The additional lumen for the guide wire may terminate at thesame position as the first and/or second lumina, or may terminatedistally beyond the distal ends of the lumina to provide additionalstability to the catheter body. In such a configuration, thesubstantially helical transition zones of the first and second luminamay be created through mechanically or thermally (e.g., with a laser)skiving the apertures within the terminal shafts of the catheter.

In still another embodiment, the first and second lumina may be splitapart along the distal portion of the septum by, for example, asplittable membrane in the septum. In this manner, the lumina may bepartially longitudinally separated from each other.

As used herein, reference to curvature or angularity with regard to theinternal walls of the lumina includes a wide range of configurations inwhich at least a portion of the internal walls of the lumen at thedistal ends thereof undergoes a transition in direction from thelongitudinal direction of the lumen to a direction angled from suchlongitudinal direction. In this fashion, fluids traveling in eitherdirection through the lumen will bear against the curved or angled wallin the transition zone in changing direction from or to a longitudinalorientation.

This change in the direction of the internal wall of the lumen in thetransition zone may be constant or may vary along some or all of thetransition zone, and may extend along two dimensions in which the flowpath changes direction substantially within a single plane, or throughthree dimensions. Preferably, the curvature or angularity of theinternal walls of the lumina extends in three dimensions and issubstantially helical. As used herein, helical patterns includespatterns that are regular and irregular and with constant or varyingdiameters along their length. So configured, the movement of fluidsthrough the transition zone imparts a helical flow pattern to suchfluids. This helical flow pattern reduces the incidence of in-planerecirculation. In the context of hemodialysis, plasmapheresis, and othertherapies which require the transport of blood, this helical flowpattern reduces the incidence of treated blood that is delivered to thepatient through the catheter to re-enter the catheter at the intakeport. The reduction of this type of recirculation allows for moreefficient blood exchange and, consequently, reduced treatment time.

The cross-sectional area and geometry of the lumina may be similar to ordifferent from each other. Preferably, the cross-sectional area of eachlumen is similarly sized in order to accommodate similar flow volumesand rates into and out from the catheter. In preferred from, thecross-sectional area of each lumen is from about 3.5 mm to about 5 ram,and more preferably from about 4.5 mm to about 5 mm. The cross-sectiongeometry of the lumina may assume a variety of shapes includingcircular, semi-circular (D-shaped), elliptical, semi-elliptical,teardrop-shaped, or curved teardrop-shaped resembling a yin-yang symbol.

The ports provided in the side walls of the distal ends of the luminamay accommodate a range of sizes and shapes including circular,semi-circular (D-shaped), elliptical, semi-elliptical, teardrop-shaped.Preferably, the ports are semi-elliptical and are from about 3 to about6 mm in maximal diameter. The terminating cavities of the first andsecond channels have a greater surface area than prior designs, such usthat shown in U.S. Pat. No. 4,808,155 by Mahurkar. This results in moreefficient exchange of fluids and blood.

The catheter of the present invention may be constructed from materialsthat are commonly used for multi-lumen catheters such as silicone orpolyurethanes including polyurethanes sold under the trademarkCarbothane® by Carboline Company of St. Louis, Mo.

In another aspect of the present invention, there is provided a methodfor exchanging fluids in a patient comprising the step of positioning acatheter of the present invention in communication with afluid-containing vessel of a patient. In preferred embodiments, theexchanged fluid comprises blood and the fluid-containing vessel of thepatient is a vein. The method of the present invention is particularlywell-suited to the performance of hemodialysis, plasmapheresis, andother therapies which require removal and return of blood from apatient. The method of the present invention may further comprise thesteps of ultrafiltration and/or venous sampling.

Turning now to the embodiment that is shown in the drawings andreferring to FIGS. 1-5, there is shown a catheter 10 having a septum 12bisecting the interior of catheter 10 to form two lumina 14 and 16. Atthe distal end of catheter 10, the lumina 14 and 16 have with curvedwalls 18 and 20 which terminate at ports 22 and 24 disposed on oppositesides of catheter 10. As shown in FIG. 2, the cross-section shape oflumina 14 and 16 are semicircular. In the catheter shown in FIGS. 1 and3-5, lumen 16 extends beyond the end of lumen 14 so as to furtherseparate the intake port 24 from outflow port 22. In operation, fluid,such as blood, enters intake port 24, changes direction as the flow offluid passes curved wall 20 through lumen 14 to tube 32 which conveysthe fluid for treatment to a device such as a dialysis machine (notshown). After treatment, the treated fluid is returned to a patientthrough tube 30 to lumen 16. At the end of lumen 16, the fluid isdeflected by curved wall 18 and out port 22 into the vessel of thepatient.

FIGS. 6A-6D illustrate an alternative embodiment of a multi-lumencatheter. The catheter 60 includes a split tip to form two lumina 61 and62. The split design eliminates the shared septum used to bisect theinterior of the catheter. Each lumen 61 and 62 has a unique wall thatdefines their shape. At the distal end of the catheter 60, the lumina 61and 62 may have with curved walls 63 and 64 which terminate at ports 65and 66 disposed on opposite sides of catheter 60. As shown by way ofexample only, the lumen 61 extends beyond the end of lumen 62 so as tofurther separate the intake port 65 from outflow port 66. In operation,fluid, such as blood, enters intake port 65, changes direction as theflow of fluid passes curved wall 63 through lumen 61 to tube 67 whichconveys the fluid for treatment to a device such as a dialysis machine(not shown). After treatment, the treated fluid is returned to a patientthrough tube 68 to lumen 62. At the end of lumen 62, the fluid isdeflected by curved wall 64 and out port 66 into the vessel of thepatient.

In operation, the lumina 61 and 62 of the catheter 60 may be attachedwith a weak adhesive to maintain structural integrity of the catheterduring operation. The adhesive may be water-soluble such that blood flowaround the catheter 60 causes the adhesive to dissolve, thereby causingat least a portion of the lumina 61 and 62 to split. For example, thecatheter 60 may be manufactured such that the last 5 cm of the catheterhave the water-soluble adhesive and thus split when the adhesivedissolves.

Based upon the intended fluid flow and acceptable disruption of thefluid, one or more side holes 69 may be included in the catheter 60. Theside holes 69 may assist in providing additional means of blood or otherfluid exchange as well as serve as a mounting point for attaching thecatheter 60 on a guide wire during insertion/removal/exchange from apatient.

The side holes 69 may be sized and positioned such that fluid flow isoptimized about the lumen tips. For example, the side holes 69 may beapproximately 1 mm in diameter, and be positioned approximately 1 cmfrom the ports 65 and 66. Alternatively, the side holes may be smaller(e.g., 0.5 mm), larger (e.g., 1.5 mm), or positioned in another location(e.g., 1.5 cm from the ports). The size and location of the side holes69 may produce changes in shear stress and blood cell residence time atthe catheter tips, and thus the optimal balance may incorporate sideholes being approximately 0.75 mm to 1.2 mm in diameter.

Using properly spaced and sized side holes, such as side holes 69, mayresult in a highly optimized catheter. For example, by using a similarcatheter to the catheter 60 as shown in FIGS. 6A-6D, fluid flow throughthe catheter may be optimized while recirculation is greatly reduced.

It should be noted that side holes 69 as shown in FIGS. 6A-6D are shownby way of example only. Additional or alternative apertures such asslits, flaps, semicircular cuts, and other similar shapes may be used.Additionally, the side holes may have a helical contour to produceadditional deflection to any fluid flowing therethrough.

As shown in FIGS. 6A-6D, the curved walls 63 and 64 define an area ofdeflection such that fluid flowing through the catheter 60 is deflected.Depending on the application of the catheter 60, and the amount ofdesired deflection, an angle of the curved walls 63 and 64 may varyaccordingly. For example, the curved walls 63 and 64 may beapproximately 54°. Alternatively, the curved walls 63 and 64 may bebetween the range of 0° and 90°. Typically, 0° and 90° may not be usedas they both have inherent drawbacks. 0° would cause no deflection tothe fluid, 90° would result in the port being perpendicular to the axialflow path of the catheter. On the input port, this could cause a vacuumforce which attaches the associated lumina to the side of a bloodvessel. While a side hole would help to alleviate any potential vacuumpressure, overall performance of the catheter would still decrease.

FIGS. 7A-7E illustrate an alternative embodiment of a multi-lumencatheter. The catheter 70 includes a stepped tip to form two lumina 71and 72. Like the split design, this design results in one lumen beinglonger than the other. The stepped tip design also eliminates a septumat the tip to bisect the interior of the catheter to form two portswhere the septum extends beyond the ports. Rather, each lumina 71 and 72has a unique curved wall that defines their shape and the flow of fluidtherethrough such that no extended septum is required to maintain fluidseparation.

At the distal end of the catheter 70, the lumina 71 and 72 may have withcurved walls 73 and 74 which terminate at ports 75 and 76 disposed onopposite sides of catheter 70. As shown by way of example only, thelumen 71 extends beyond the end of lumen 72, thereby forming a steppedtip design and further separating the intake port 75 from outflow port76. As before, in operation, fluid, such as blood, enters intake port75, changes direction as the flow of fluid passes curved wall 73 throughlumen 71 to tube 77 which conveys the fluid for treatment to a devicesuch as a dialysis machine (not shown). After treatment, the treatedfluid is returned to a patient through tube 78 to lumen 72. At the endof lumen 72, the fluid is deflected by curved wall 74 and out port 76into the vessel of the patient.

Similar to the discussion above in reference to FIGS. 6A-6D, one or moreside holes (not shown in FIGS. 7A-7E) may be included in the catheter70. The side holes 79 may assist in providing additional means of bloodor other fluid exchange as well as serve as a mounting point forattaching the catheter 70 on a guide wire during catheter insertionand/or removal and/or exchange from a patient.

As shown in FIGS. 7A-7E, the curved walls 73 and 74 define an area ofdeflection such that fluid flowing through the catheter 70 is deflected.Depending on the application of the catheter 70, and the amount ofdesired deflection, an angle of the curved walls 73 and 74 may varyaccordingly. For example, the curved walls 73 and 74 may beapproximately 54°. Alternatively, the curved walls 73 and 74 may bebetween the range of 0° and 90°. Typically, 0° and 90° may not be usedas they both have inherent drawbacks. 0° would cause no deflection tothe fluid. 90° would result in the port being perpendicular to the axialflow path of the catheter. On the input port, this could cause a vacuumforce which attaches the associated lumina to the side of a bloodvessel. While a side hole would help to alleviate any potential vacuumpressure, overall performance of the catheter would still decrease.

FIGS. 8A-8E illustrate an alternative embodiment of a multi-lumencatheter. The catheter 80 includes a symmetrical tip where two lumina 81and 82 terminate at the same point such that the ports are adjacent.Additionally, unlike common prior art, the symmetrical tip design asshown herein also eliminates the septum extending beyond the distal endsof the lumina 81 and 82 such that the septum extends beyond the ports.Rather, the septum is trimmed such that it terminates concurrent to theports. Each lumen 81 and 82 has a unique curved wall that defines theirshape and the flow of fluid therethrough such that no extended septum isrequired to maintain fluid separation. As shown in FIG. 8D, thecross-section shape of lumina 81 and 82 are semicircular.

At the distal end of the catheter 80, the lumina 81 and 82 may have withcurved walls 83 and 84 which terminate at ports 85 and 86 disposed onopposite sides of catheter 80. In this symmetrical tip embodiment, thelumen 81 extends to same point as the lumen 82, thereby forming asymmetrical tip design. As before, in operation, fluid, such as blood,enters intake port 85, changes direction as the flow of fluid passescurved wall 83 through lumen 81 to tube 87 which conveys the fluid fortreatment to a device such as a dialysis machine (not shown). Aftertreatment, the treated fluid is returned to a patient through tube 88 tolumen 82. At the end of lumen 82, the fluid is deflected by curved wall84 and out port 86 into the vessel of the patient. By providing thecurved walls 83 and 84 to deflect the fluid, the design eliminates theseptum extending beyond the ports while still maintaining a low level offluid from the out port 86 mixing with fluid entering the intake port85.

Similar to the discussion above in reference to FIGS. 6A-6D, one or moreside holes 89 may be included in the catheter 80. The side holes 89 mayassist in providing additional means of blood or other fluid exchange aswell as serve as a mounting point for attaching the catheter 80 on aguide wire during insertion and/or removal and/or exchange from apatient.

The side holes 89 may be sized and positioned such that fluid flow isoptimized about the lumen tips. For example, the side holes 89 may beapproximately 1 mm in diameter, and be positioned approximately 1 cmfrom the ports 85 and 86. Alternatively, the side holes may be smaller(e.g., 0.5 mm), larger (e.g., 1.5 mm), or positioned in another location(e.g., 1.5 cm from the ports). The size and location of the side holes89 may produce changes in shear stress and blood cell residence time atthe catheter tips, and thus the optimal balance may incorporate sideholes being approximately 0.75 mm to 1.2 mm in diameter.

Using properly spaced and sized side holes, such as side holes 89, mayresult in a highly optimized catheter. For example, by using a similarcatheter to the catheter 80 as shown in FIGS. 8A-8E, fluid flow throughthe catheter may be optimized while recirculation is greatly reduced.

It should be noted that side holes 89 as shown in FIGS. 8A-8E are shownby way of example only. Additional or alternative apertures such asslits, flaps, semicircular cuts, and other similar shapes may be used.Additionally, the side holes themselves may have a helical contour toproduce additional deflection to any fluid flowing therethrough.

As shown in FIGS. 8A-8E, the curved walls 83 and 84 define an area ofdeflection such that fluid flowing through the catheter 80 is deflected.Depending on the application of the catheter 80, and the amount ofdesired deflection, an angle of the curved walls 83 and 84 may varyaccordingly. For example, the curved walls 83 and 84 may beapproximately 54°. Alternatively, the curved walls 83 and 84 may bebetween the range of 0° and 90°. Typically, 0° and 90° may not be usedas they both have inherent drawbacks. 0° would cause no deflection tothe fluid. 90° would result in the port being perpendicular to the axialflow path of the catheter. On the input port, this could cause a vacuumforce which attaches the associated lumina to the side of a bloodvessel. While a side hole would help to alleviate any potential vacuumpressure, overall performance of the catheter would still decrease.

FIGS. 9A-9D illustrate an alternative embodiment of a multi-lumencatheter. The catheter 90 includes a symmetrical tip where two lumina 91and 92 terminate at the same point such that the ports are adjacent.Additionally, unlike common prior art, the symmetrical tip design asshown herein also eliminates the septum extending beyond the distal endsof the lumina 91 and 92 such that the septum extends beyond the ports.Rather, the septum is trimmed such that it terminates concurrent to theports. Each lumen 91 and 92 has a unique curved wall that defines theirshape and the flow of fluid therethrough such that no extended septum isrequired to maintain fluid separation. As shown in FIG. 9D, thecross-section shape of lumina 91 and 92 are semicircular.

Unlike the catheter 80 as shown in FIGS. 8A-8E, the catheter 90 includesa spiral twist at the distal end. As shown in FIG. 9C, the twistedportion 100 of the catheter 90 with the spiral twist may be rotatedbetween 1° and 359°, however, an optimum value would be somewhere in themiddle of this range, depending on the viscosity and volume of fluidbeing moved through the catheter. For example, for a catheter to be usedfor human dialysis, a rotation of about 135° within about 4 cm extendingfrom the distal end of the catheter may be optimal. Alternatively, arange of about 120° to about 150° within an approximate 1 cm to 5 cmextending from the distal end of the catheter may be optimal.

At the distal end of the catheter 90, the lumina 91 and 92 may have withcurved walls 93 and 94 which terminate at ports 95 and 96 disposed onopposite sides of catheter 90. In this symmetrical tip embodiment, thelumen 91 extends to same point as the lumen 92, thereby forming asymmetrical tip design. As before, in operation, fluid, such as blood,enters intake port 95, changes direction as the flow of fluid passescurved wall 93 and through the twisted portion 100 of lumen 91 to tube97 which conveys the fluid for treatment to a device such as a dialysismachine (not shown). After treatment, the treated fluid is returned to apatient through tube 98 to lumen 92. At the end of lumen 92, the fluidis deflected by the twisted portion 100 and the curved wall 94, andpasses through out port 96 into the vessel of the patient. By providingthe curved walls 93 and 94 and the twisted portion 100 to deflect thefluid, this design eliminates the septum extending beyond the portswhile still maintaining a low level of fluid from the out port 96 mixingwith fluid entering the intake port 95.

Similar to the discussion above in reference to FIGS. 6A-6D, one or moreside holes 99 may be included in the catheter 90. The side holes 99 mayassist in providing additional means of blood or other fluid exchange aswell as serve as a mounting point for attaching the catheter 90 on aguide wire during insertion and/or removal and/or exchange from apatient.

The side holes 99 may be sized and positioned such that fluid flow isincreased about the lumen tips. For example, the side holes 99 may beapproximately 1 mm in diameter, and be positioned approximately 1 cmfrom the ports 95 and 96. Alternatively, the side holes may be smaller(e.g., 0.5 mm), larger (e.g., 1.5 mm), or positioned in another location(e.g., 1.5 cm from the ports). The size and location of the side holes99 may produce changes in shear stress and blood cell residence time atthe catheter tips, and thus the optimal balance may incorporate sideholes being approximately 0.75 mm to 1.2 mm in diameter.

Using properly spaced and sized side holes, such as side holes 99, mayresult in a highly optimized catheter. For example, by using a similarcatheter to the catheter 90 as shown in FIGS. 9A-9D, fluid flow throughthe catheter may be optimized while recirculation is greatly reduced.

It should be noted that side holes 99 as shown in FIGS. 8A-8E are shownby way of example only. Additional or alternative apertures such asslits, flaps, semicircular cuts, and other similar shapes may be used.Additionally, the side holes themselves may have a helical contour toproduce additional deflection to any fluid flowing therethrough.

As shown in FIGS. 9A-9D, the curved walls 93 and 94 define an area ofdeflection such that fluid flowing through the catheter 90 is deflected.Depending on the application of the catheter 90, and the amount ofdesired deflection, an angle of the curved walls 93 and 94 may varyaccordingly. For example, the curved walls 93 and 94 may beapproximately 54°. Alternatively, the curved walls 93 and 94 may bebetween the range of 0° and 90°. Typically, 0° and 90° may not be usedas they both have inherent drawbacks. 0° would cause no deflection tothe fluid. 90° would result in the port being perpendicular to the axialflow path of the catheter. On the input port, this could cause a vacuumforce which attaches the associated lumina to the side of a bloodvessel. While a side hole would help to alleviate any potential vacuumpressure, overall performance of the catheter would still decrease.

Although the invention has been described in language specific tostructural features and/or methodological acts, it is to be understoodthat the invention defined in the appended claims is not necessarilylimited to the specific features or acts described. Rather, the specificfeatures and acts are disclosed as exemplary forms of implementing theclaimed invention.

Various of the above-disclosed and other features and functions, oralternatives thereof, may be combined into many other different systemsor applications. Various presently unforeseen or unanticipatedalternatives, modifications, variations or improvements therein may besubsequently made by those skilled in the art, each of which is alsointended to be encompassed by the disclosed embodiments.

I claim:
 1. A catheter for placement within a vessel of a patientcomprising: an elongated catheter body haying a proximal end and adistal end; and a septum extending longitudinally through at least aportion of the interior of the catheter body, thereby dividing theinterior of the catheter body into a first lumen and a second lumen;wherein each of the first lumen and the second lumen comprise curvedinternal walls at the distal end of the catheter that terminate at portslocated on opposing sides of the catheter body such that fluid flowingthrough the ports is deflected within a single plane.
 2. The catheter ofclaim 1, wherein a distal end of the first lumen extends beyond a distalend of the second lumen.
 3. The catheter of claim 2, wherein the distalend of the first lumen extends from about 2 cm to about 3 cm beyond thedistal end of the second lumen.
 4. The catheter of claim 1, wherein thefirst lumen and the second lumen are split apart.
 5. The catheter ofclaim 1, wherein the first lumen and the second lumen are the samelength such that the ports are adjacent to one another.
 6. The catheterof claim 1, wherein at least one of the first lumen and the second lumencomprises at least one aperture.
 7. The catheter of claim 6, wherein theat least one aperture is a side hole.
 8. The catheter of claim 1,wherein at least a portion of the catheter is spirally twisted, therebyfurther deflecting fluid flowing through the catheter.
 9. A catheter forplacement within a vessel of a patient comprising: an elongated catheterbody having a proximal end and a distal end; a first lumen comprising afirst internal wall at the distal end of the catheter that forms aninput port, wherein the first internal wall is curved such that fluidflowing through the input port is deflected within a single plane; asecond lumen comprising a second internal wall at the distal end of thecatheter that forms an out port, wherein the second internal wall iscurved such that fluid flowing through the out port is deflected withina single plane; and a septum extending longitudinally through at least aportion of the interior of the catheter body, thereby dividing theinterior of the catheter body into the first lumen and the second lumen.10. The catheter of claim 9, wherein a distal end of the first lumenextends beyond a distal end of the second lumen.
 11. The catheter ofclaim 10, wherein the distal end of the first lumen extends from about 2cm to about 3 cm beyond the distal end of the second lumen.
 12. Thecatheter of claim 9, wherein the first lumen and the second lumen aresplit apart.
 13. The catheter of claim 9, wherein the first lumen andthe second lumen are the same length such the input port and the outport are adjacent to one another.
 14. The catheter of claim 9, whereinat least one of the first lumen and the second lumen comprises at leastone aperture.
 15. The catheter of claim 14, wherein the at least oneaperture is a side hole.
 16. The catheter of claim 9, wherein at least aportion of the catheter is spirally twisted, thereby further deflectingfluid flowing through the catheter.